In the past, there has been known a system that operates by accessorily using power generated by a power generator that converts natural energy into power. There has been known a technique of operating a task processing in such a system only when an amount of energy required for the task processing is able to be covered by an auxiliary power supply unit that stores power generated by a power generator.
However, in the conventional technique, since power required in a system (for example, power consumed in a memory or the like) other than power required for a task processing until completion of the task processing is not considered at all, there is also a fear that power supply will be lost in the middle of the task processing.